Update logging documentation

RELEASE.md

@@ -16,11 +16,15 @@
 
 ## Major features and improvements
 * Added `abfss` to list of cloud protocols, enabling abfss paths.
+* Kedro now uses the [https://github.com/Textualize/rich](Rich) library to format terminal logs.
+* The file `conf/base/logging.yml` is now optional. See [our documentation](https://kedro.readthedocs.io/en/0.18.2/logging/logging.html) for details.
 
 ## Bug fixes and other changes
 * Bumped `pyyaml` upper-bound to make Kedro compatible with the [pyodide](https://pyodide.org/en/stable/usage/loading-packages.html#micropip) stack.
 * Updated project template's Sphinx configuration to use `myst_parser` instead of `recommonmark`.
 * Reduced number of log lines by changing the logging level from `INFO` to `DEBUG` for low priority messages.
+* Kedro's framework-side logging configuration no longer performs file-based logging. Hence superfluous `info.log`/`errors.log` files are no longer created in your project root, and running Kedro on read-only file systems such as Databricks Repos is now possible.
+* The `root` logger is now set to the Python default level of `WARNING` rather than `INFO`. Kedro's logger is still set to emit `INFO` level messages.
 
 ## Upcoming deprecations for Kedro 0.19.0
 * `kedro.extras.ColorHandler` will be removed in 0.19.0.

docs/source/deployment/databricks.md

@@ -2,6 +2,10 @@
 
 This tutorial uses the [PySpark Iris Kedro Starter](https://github.com/kedro-org/kedro-starters/tree/main/pyspark-iris) to illustrate how to bootstrap a Kedro project using Spark and deploy it to a [Databricks cluster on AWS](https://databricks.com/aws).
 
+```{note}
+If you are using [Databricks Repos](https://docs.databricks.com/repos/index.html) to run a Kedro project then you should [disable file-based logging](../logging/logging.md#disable-file-based-logging). This prevents Kedro from attempting to write to the read-only file system.
+```
+
 ## Prerequisites
 
 * New or existing [AWS account](https://aws.amazon.com/premiumsupport/knowledge-center/create-and-activate-aws-account/) with administrative privileges

docs/source/logging/logging.md

@@ -1,14 +1,58 @@
 # Logging
 
-Kedro uses, and facilitates, the use of Python’s `logging` library by providing a default logging configuration. This can be found in `conf/base/logging.yml` in every project generated using Kedro’s CLI `kedro new` command.
+Kedro uses [Python's `logging` library](https://docs.python.org/3/library/logging.html). Configuration is provided as a dictionary according to the [Python logging configuration schema](https://docs.python.org/3/library/logging.config.html#logging-config-dictschema) in two places:
+1. [Default configuration built into the Kedro framework](https://github.com/kedro-org/kedro/blob/main/kedro/config/logging.yml). This cannot be altered.
+2. Your project-side logging configuration. Every project generated using Kedro's CLI `kedro new` command includes a file `conf/base/logging.yml`. You can alter this configuration and provide different configurations for different run environment according to the [standard Kedro mechanism for handling configuration](../kedro_project_setup/configuration.md).
 
-## Configure logging
+```{note}
+Providing project-side logging configuration is entirely optional. You can delete the `conf/base/logging.yml` file and Kedro will run using the framework's built in configuration.
+```
+
+Framework-side and project-side logging configuration are loaded through subsequent calls to [`logging.config.dictConfig`](https://docs.python.org/3/library/logging.config.html#logging.config.dictConfig). This means that, when it is provided, the project-side logging configuration typically _fully overwrites_ the framework-side logging configuration. [Incremental configuration](https://docs.python.org/3/library/logging.config.html#incremental-configuration) is also possible if the `incremental` key is explicitly set to `True` in your project-side logging configuration.
+
+## Default framework-side logging configuration
+
+Kedro's [default logging configuration](https://github.com/kedro-org/kedro/blob/main/kedro/config/logging.yml) defines a handler called `rich` that uses the [Rich logging handler](https://rich.readthedocs.io/en/stable/logging.html) to format messages and handle exceptions.
+
+By default, Python only shows logging messages at level `WARNING` and above. Kedro's logging configuration specifies that `INFO` level messages from Kedro should also be emitted. This makes it easier to track the progress of your pipeline when you perform a `kedro run`.
+
+## Project-side logging configuration
+
+In addition to the `rich` handler defined in Kedro's framework, the [project-side `conf/base/logging.yml`](https://github.com/kedro-org/kedro/blob/main/kedro/templates/project/%7B%7B%20cookiecutter.repo_name%20%7D%7D/conf/base/logging.yml) defines three further logging handlers:
+* `console`: show logs on standard output (typically your terminal screen) without any rich formatting
+* `info_file_handler`: write logs of level `INFO` and above to `logs/info.log`
+* `error_file_handler`: write logs of level `ERROR` and above to `logs/error.log`
+
+The logging handlers that are actually used by default are `rich`, `info_file_handler` and `error_file_handler`.
+
+The project-side logging configuration also ensures that [logs emitted from your project's logger](#perform-logging-in-your-project) should be shown if they are `INFO` level or above (as opposed to the Python default of `WARNING`).
+
+We now give some common examples of how you might like to change your project's logging configuration.
 
-You can customise project logging in `conf/<env>/logging.yml` using [standard Kedro mechanisms for handling configuration](../kedro_project_setup/configuration.md). The configuration should comply with the guidelines from the `logging` library. Find more about it in [the documentation for `logging` module](https://docs.python.org/3/library/logging.html).
+### Disable file-based logging
 
-## Use logging
+You might sometimes need to disable file-based logging, e.g. if you are running Kedro on a read-only file system such as [Databricks Repos](https://docs.databricks.com/repos/index.html). The simplest way to do this is to delete your `conf/base/logging.yml` file. The `logs` directory can then also be safely removed. With no project-side logging configuration specified, Kedro uses the default framework-side logging configuration, which does not include any file-based handlers.
 
-After reading and applying project logging configuration, `kedro` will start emitting the logs automatically. To log your own code, you are advised to do the following:
+Alternatively, if you would like to keep other configuration in `conf/base/logging.yml` and just disable file-based logging, then you can remove the file-based handlers from the `root` logger as follows:
+```diff
+ root:
+-  handlers: [console, info_file_handler, error_file_handler]
++  handlers: [console]
+```
+
+### Use plain console logging
+
+To use plain rather than rich logging, swap the `rich` handler for the `console` one as follows:
+
+```diff
+ root:
+-  handlers: [rich, info_file_handler, error_file_handler]
++  handlers: [console, info_file_handler, error_file_handler]
+```
+
+## Perform logging in your project
+
+To perform logging in your own code (e.g. in a node), you are advised to do as follows:
 
 ```python
 import logging
@@ -19,19 +63,10 @@ log.info("Send information")
 ```
 
 ```{note}
-The name of a logger corresponds to a key in the `loggers`  section in `logging.yml` (e.g. `kedro.io`). See [Python's logging documentation](https://docs.python.org/3/library/logging.html#logger-objects) for more information.
+The name of a logger corresponds to a key in the `loggers`  section in `logging.yml` (e.g. `kedro`). See [Python's logging documentation](https://docs.python.org/3/library/logging.html#logger-objects) for more information.
 ```
 
-## Logging for `anyconfig`
-
-By default, [anyconfig](https://github.com/ssato/python-anyconfig) library that is used by `kedro` to read configuration files emits a log message with `INFO` level on every read. To reduce the amount of logs being sent for CLI calls, default project logging configuration in `conf/base/logging.yml` sets the level for `anyconfig` logger to `WARNING`.
-
-If you would like `INFO` level messages to propagate, you can update `anyconfig` logger level in `conf/base/logging.yml` as follows:
-
-```yaml
-loggers:
-    anyconfig:
-        level: INFO  # change
-        handlers: [console, info_file_handler, error_file_handler]
-        propagate: no
+You can take advantage of rich's [console markup](https://rich.readthedocs.io/en/stable/markup.html) when enabled in your logging calls:
+```python
+log.error("[bold red blink]Important error message![/]", extra={"markup": True})
 ```